Optical fiber cable with impact resistant buffer tube

Abstract

A crush resistant optical cable and/or crush resistant optical fiber buffer tube are provided. The cable generally includes a tube having at least one layer formed from a first material and an optical fiber located within a channel of the first tube. The buffer tube is configured to protect optical fibers from crush or impact events through a cushioning action. For example, the first material may be a polymer material having modulus of elasticity of less than 200 MPa, and the layer of the tube acts as a compliant cushioning layer at least partially contacting and surrounding an outer surface of the optical fiber when radially directed forces are applied to the outer surface of the tube.

What is claimed is: 
     
       1. A crush resistant optical fiber buffer tube comprising:
 an outer surface; 
 an inner surface; 
 a channel defined by the inner surface; 
 a first layer formed from a first material, the first material of the first layer defining the inner surface; 
 a second layer formed from a second material, located around and outside of the first layer; 
 and 
 a plurality of optical fibers located within the channel, wherein each optical fiber includes an optical core surrounded by cladding of a different refractive index than the optical core, the cladding surrounded by a fiber coating layer; 
 wherein the first material has a modulus of elasticity in the elastic region that is less than 200 MPa and the modulus of elasticity in the elastic region of the material of the fiber coating layer is greater than 500 MPa; 
 wherein a total radial thickness of the buffer tube between the inner surface and the outer surface is between 0.25 mm and 0.5 mm, wherein a radial thickness of the first layer is at least 30% of a total radial thickness of the buffer tube; 
 wherein the modulus of elasticity of the second material is greater than 500 MPa, wherein the modulus of elasticity of the first material is less than 10 MPa, wherein the first material of the first layer is at least one of a thermoplastic olefin, a thermoplastic urethane, a thermoplastic copolyester and a thermoplastic polyamide, wherein the second material of the second layer is polypropylene, wherein the material of the fiber coating layer is a UV cured polymer layer, wherein the buffer tube has an outer diameter of between 1.5 mm and 3.5 mm, wherein the channel has a cross-sectional area, wherein the cross-sectional area of the channel is at least twice a total cross-sectional area of all of the plurality of optical fibers located within the channel. 
 
     
     
       2. An impact resistant optical cable comprising:
 a cable body including an inner surface defining a channel within the cable body; and 
 a core element located in the channel of the cable body, the core element comprising:
 a tube including an outer surface, an inner surface and a channel defined by the inner surface of the tube, wherein the tube includes a first layer formed from a polymer material, the polymer material of the first layer defining the inner surface of the tube, and wherein the tube includes a second layer formed from a second material, the second layer located around and outside of the first layer; and 
 at least one coated optical fiber located within the channel of the tube; 
 
 wherein the first layer of the tube is configured such that an impact on the tube results in a force imparted by the tube on the at least one coated optical fiber corresponding to the impaction parameter p of less than or equal to 2800 m −1 ; and 
 wherein the modulus of elasticity of the second material is greater than 500 MPa, wherein the modulus of elasticity of the first material is less than 10 MPa, wherein the first material of the first layer is at least one of a thermoplastic olefin, a thermoplastic urethane, a thermoplastic copolyester and a thermoplastic polyamide, wherein the second material of the second layer is polypropylene, wherein the material of the fiber coating layer is a UV cured polymer layer, wherein the tube has an outer diameter of between 1.5 mm and 3.5 mm, wherein the channel has a cross-sectional area, wherein the cross-sectional area of the channel is at least twice a total cross-sectional area of all of the plurality of optical fibers located within the channel. 
 
     
     
       3. The impact resistant optical cable of  claim 2 , wherein 100 m −1 ≤ρ≤2800 m −1 . 
     
     
       4. The impact resistant optical cable of  claim 2 , wherein 100 m −1 ≤ρ≤1000 m  −1 . 
     
     
       5. The impact resistance optical cable of  claim 2 , wherein polymer material of the first layer has a modulus of elasticity in the elastic region of less than 200 MPa, wherein the first layer has a thickness less than 0.75 mm.